Re: [PATCH 20/24] Correct handling of interrupt injection

[Avi Kivity <avi@redhat.com>]

On 06/13/2010 03:32 PM, Nadav Har'El wrote:
> When KVM wants to inject an interrupt, the guest should think a real interrupt
> has happened. Normally (in the non-nested case) this means checking that the
> guest doesn't block interrupts (and if it does, inject when it doesn't - using
> the "interrupt window" VMX mechanism), and setting up the appropriate VMCS
> fields for the guest to receive the interrupt.
>
> However, when we are running a nested guest (L2) and its hypervisor (L1)
> requested exits on interrupts (as most hypervisors do), the most efficient
> thing to do is to exit L2, telling L1 that the exit was caused by an
> interrupt, the one we were injecting; Only when L1 asked not to be notified
> of interrupts, we should to inject it directly to the running guest L2 (i.e.,
> the normal code path).
>
> However, properly doing what is described above requires invasive changes to
> the flow of the existing code, which we elected not to do in this stage.
> Instead we do something more simplistic and less efficient: we modify
> vmx_interrupt_allowed(), which kvm calls to see if it can inject the interrupt
> now, to exit from L2 to L1 before continuing the normal code. The normal kvm
> code then notices that L1 is blocking interrupts, and sets the interrupt
> window to inject the interrupt later to L1. Shortly after, L1 gets the
> interrupt while it is itself running, not as an exit from L2. The cost is an
> extra L1 exit (the interrupt window).
>
>    

That's a little sad.

>
>   	cpu_based_vm_exec_control = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL);
>   	cpu_based_vm_exec_control |= CPU_BASED_VIRTUAL_INTR_PENDING;
> @@ -3718,6 +3738,13 @@ static int nested_vmx_vmexit(struct kvm_
>
>   static int vmx_interrupt_allowed(struct kvm_vcpu *vcpu)
>   {
> +	if (to_vmx(vcpu)->nested.nested_mode&&  nested_exit_on_intr(vcpu)) {
> +		if (to_vmx(vcpu)->nested.nested_run_pending)
> +			return 0;
> +		nested_vmx_vmexit(vcpu, true);
> +		/* fall through to normal code, but now in L1, not L2 */
> +	}
> +
>    

What exit is reported here?

-- 
error compiling committee.c: too many arguments to function